We synthesized three semicrystalline polymers (PTTBTBO, PDTBTBO, and P2FDTBT(BO)) by modulating the intra- and intermolecular noncovalent Coulombic interactions and investigated their photovoltaic characteristics under various light intensities. Low series (R-s) and high shunt (R-sh) resistances are essential prerequisites for good device properties under standard illumination (100 mW cm(-2)). Considering these factors, among three polymers, PDTBTBO polymer solar cells (PSCs) exhibited the most desirable Characteristics, with peak power conversion efficiencies (PCE) of 7.52 and 9.60% by being blended with PC71BM under standard and dim light (2.5 mW cm(2)), respectively. P2FDTBT(BO) PSCs exhibited a low PCE of 3.69% under standard light due to significant charge recombination with high R-s (9.42 Omega cm(2)). However, the PCE was remarkably improved by 2.3 times (8.33% PCE) under dim light, showing negligible decrease in open-circuit voltage and remarkable increase in fill factor, which is due to an exceptionally high R-sh of over 1000 k Omega cm(2). R-s is less significant under dim light because the generated current is too small to cause noticeable R-s-induced voltage losses. Instead, high R-sh becomes more important to avoid leakage currents. This work provides important tips to further optimize PSCs for indoor applications with low-power electronic devices such as Internet of things sensors.